This invention relates to punch presses in general and, in particular, to a portable, power driven punch press suitable for bending, cutting, perforating, or otherwise working on steel frame members at sites of construction.
Hydraulic punch presses of the kind under consideration were long separate from hydraulic power units comprising a pump and a drive motor. The pump was communicated with the press via a flexible conduit system. Such conventional punch press systems were difficult of handling, particularly at construction sites where they had to be often carried from one place to another. Another objection to such known machines is that their frames, comprised of four columns in some instances, can interfere with the loading, unloading, and punching of blanks of bulky size or complex shape.
In order to remedy these drawbacks Japanese Unexamined Utility Model Publication No. 63-138921 suggests an integrated hydraulic punch press in which the hydraulic power unit is coupled directly to a hydraulic cylinder. This punch press also features a frame that is in the shape of a C when the press is seen in a side view, with the hydraulic cylinder mounted upstandingly to the upper horizontal limb, or overarm, of the C frame. The portability of this integrated punch press is of course much better than that of the more conventional one. Its operability is greatly enhanced, too. Since the C frame is open both forwardly and laterally of the machine, the blank can be loaded and unloaded from the front of the press.
The known integrated punch press has its own weaknesses, however. The machine was devoted exclusively to the creation of holes, so that additional machines had to be brought to construction sites for other operations such as cutting and bending.
Another disadvantage arose from the fact that the hydraulic power unit was disposed vertically in line with the hydraulic cylinder, adding substantially to the total height of the machine. The tall punch press brings about an inconvenience when it is modified to perform bending. Assume that an L sectioned steel strip is to be bent at right angles at three longitudinally spaced points thereon into a rectangular frame, as is frequency required at construction sites. Then, depending upon the frame size required, the upstanding hydraulic power unit may interfere with the blank during the bending of the last point thereon.